In Germany in the 1950s and 1960s a petrol-fired heater was available as an after-market accessory, chiefly for air-cooled cars. It was for example listed as a factory option for Porsche 356 cars up to and including the 356C, and was called the "Eberspacher" (or East Wind) heater.Since it was offered as an accessory, it may well have been fitted to the early Goliath cars, but I am not aware that the factory offered it as an approved option.